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Zagros forests have the greatest impact on soil and water protection in western Iran. Despite this, a significant part of these forests, especially in Ilam province, have suffered a lot due to the phenomenon of oak decline. The first and most fundamental thing a person must know when combating this issue is the distribution of these areas in forests. Therefore, using the parameters affecting the decline in the forests of Ilam province and based on fuzzy logic, a map of susceptible to oak decline areas was prepared. In this study, the parameters of temperature and precipitation, slope, aspect, altitude, distance from farmlands, roads and forest density were selected as effective parameters and fuzzy gamma overlap method was used. The results showed that more than 77% of the oak forests in the province are highly and extremely susceptible to the decline. This confirms the need for rapid action to plan and protect these forests. In addition, the fuzzy method is proposed, which is considered as a fast and efficient method in preparing such maps for other areas.

Cork oak decline and mortality are increasingly prevalent in the Mediterranean basin. This require particular attention due to the great economic value of this plant species. Biscogniauxia mediterranea is one of the most common pathogens highly associated to cork oak decline. However, documentation on its incidence is still scarce, especially in Tunisia. In this context, our research aimed at detecting its presence in Tunisian natural cork oak forests and assessing factors influencing its occurrence. Investigations were carried out in six forests in northwestern Tunisia. Dendrometric parameters of trees, ecological factors (rainfall, temperature, and altitude), and the presence of B. mediterranea as pathogen were determined. The endophytic presence of this fungus was also established. It was detected in all investigated forests, with significantly different frequencies, and was reported to be related to the dendrometric structure of the cork oak trees. On the other hand, the presence of B. mediterranea as pathogen was only detected in Ain Beya and Ain Sarouia forests. It was very limited with 4% of trees per site showing the disease signs. In conclusion, measures to prevent the dispersal of B. mediterranea throughout other cork oak forests shall be implemented in order to conserve such valuable forest resources.

Stereoselective syntheses of new pyranopyrans that are related to the natural product diplopyrone, which is a phytotoxin implicated in cork oak decline, have been achieved from carbohydrate starting materials in two approaches that are based on

The multiplex real‐time PCR assay can simultaneously detect four bacterial species associated with Acute Oak Decline (AOD) from stem bleed swabs, eliminating the need for destructive sampling of high‐value trees to isolate bacteria.

Since 2013, pedunculate oak (Quercus robur L.) mortality has been observed in the Ardennes region of Belgium. We aimed to understand the current decline by retrospectively (1945–2015) studying radial growth patterns of trees classified by three health statuses (reference, declining, and dying) and by linking them to abiotic and biotic hazard history, which we recorded and quantified. Our results show that oak mortality in the Ardennes is a long-term process, with 1987 as a tipping point for growth trajectories of declining and dying trees. That year was preceded by two growth crises (1976–1981 and 1984–1987), and it falls within the last major episode of oak decline in Belgium. Among hazards, very cold winters and caterpillar outbreaks have significant impacts on growth-pattern differentiation. Apart from 1976, extreme drought is still rare; however, mild spring droughts, especially in the years n − 1 and n − 2, explain some of the growth loss relative to the reference trees. Finally, masting appears to be an important contributing factor for the death of weakened trees. Given the direct and delayed impacts of the extreme drought of 1976 and subsequent water balance impairment due to winter frosts and mild spring droughts, the health of pedunculate oak is giving cause for concern in the context of climate change.

Ash dieback, acute oak decline (AOD), and Xylella Fastidiosa are emerging infectious diseases (EIDs) that have spread rapidly in European forests during the last decade. Quarantine measurements have mostly failed to repress the outbreaks and millions of trees have already been infected. Identifying infected trees in a nondestructive manner is of high importance for monitoring, managing, and preventing EIDs. The aim of this article is to examine the capabilities of ground penetrating radar (GPR) on evaluating the internal structure of tree trunks and detecting tree decay associated with EIDs. Traditionally used processing schemes tuned for GPR line acquisitions are modified accordingly to be compatible with the new measurement configurations. In particular, a detection framework is presented based on a modified Kirchhoff and a reverse-time migration. Both of the aforementioned methodologies are compatible with measurements taken along closed irregular curves assuming a homogeneous permittivity distribution. To that extent, prior to migration, a novel focal criterion is used that estimates the bulk permittivity of the host medium from the measured B-scans. The suggested detection scheme is successfully tested on both numerical and laboratory measurements, indicating that GPR has the potential to become a coherent and practical tool for detecting tree decay associated with EIDs.

© 2019 The Royal Entomological Society 1. Dark diversity represents the set of species that can potentially inhabit a given area under particular ecological conditions, but are currently ‘missing’ from a site. This concept allows characterisation of the mechanisms determining why species are sometimes absent from an area that seems ecologically suitable for them. 2. The aim of this study was to determine the dark diversity of hoverflies in south-eastern Europe and to discuss the role of different functional traits that might increase the likelihood of species contributing to dark diversity. Based on expert opinion, the Syrph the Net database and known occurrences of species, the study estimated species pools, and observed and dark diversities within each of 11 defined vegetation types for 564 hoverfly species registered in south-eastern Europe. To detect the most important functional traits contributing to species being in dark diversity across different vegetation types, a random forest algorithm and respective statistics for variable importance were used. 3. The highest dark diversity was found for southwest Balkan sub-Mediterranean mixed oak forest type, whereas the lowest was in Mediterranean mixed forest type. Three larval feeding modes (saproxylic, and phytophagous on bulbs or roots) were found to be most important for determining the probability of a species contributing to hoverfly dark diversity, based on univariate correlations and random forest analysis. 4. This study shows that studying dark diversity might provide important insights into what drives community assembly in south-eastern European hoverflies, especially its missing components, and contributes to more precise conservation prioritisation of both hoverfly species and their habitats.

Holm oak is a key tree species in Mediterranean ecosystems, whose populations have been increasingly threatened by oak decline syndrome, a disease caused by the combined action of Phytophthora cinnamomi and abiotic stresses. The aim of the present study was to produce holm oak plants that overexpress the Ginkbilobin-2 homologous domain gene (Cast_Gnk2-like) that it is known to possess antifungal properties. Proembryogenic masses (PEMs) isolated from four embryogenic lines (Q8, E2, Q10-16 and E00) were used as target explants. PEMs were co-cultured for 5 days with Agrobacterium EHA105pGnk2 and then cultured on selective medium containing kanamycin (kan) and carbenicillin. After 14 weeks on selective medium, the transformation events were observed in somatic embryos of lines Q8 and E2 and a total of 4 transgenic lines were achieved. The presence of the Cast_Gnk2-like gene on transgenic embryos was verified by PCR, and the number of transgene copies and gene expression was estimated by qPCR. Transgenic plants were obtained from all transgenic lines after cold storage of the somatic embryos for 2 months and subsequent transfer to germination medium. In an in vitro tolerance assay with the pathogen P. cinnamomi, we observed that transgenic plants were able to survive longer than wild type., This investigation was partly supported by the Spanish govern through the projects AGL2016-76143-C4-4-R and PID2020-112627RB-C33 (MICINN), and by the Portuguese govern through the projects PTDC/AGR-CFL/101707/2008, LISBOA-01-0145-FEDER-028760 and Grants to SS supported by Fundação para a Ciência e a Tecnologia (FCT/MCTES/PIDDAC, Portugal) through postdoctoral fellowship SFRH/BPD/108653/2015 and the work contract 2477 of the contract program 12345/20181 defined by DL nr. 57/2016, as well as through research funds awarded to RM (PTDC/BIA-FBT/28170/2017) and to BioISI (UIDB/04046/2020 and UIDP/04046/2020).

The dehesa is a traditional agrosilvopastoral ecosystem characterized by a savanna-like structure. It has been in decline since the middle of the last century, in particular in agricultural environments where it has been relegated to isolated forests. This paper presents a study into the reduction over the past 50 years. One of the main causes of this decline has been identified as xylophagous insects, specifically the wood borer Cerambyx welensii Kuster (Coleoptera: Cerambycidae). Based on estimations in both the population size, using Jolly Seber models, and the level of tree injury, using a single-index model, the study investigates the role the insect has played in the decline of the dehesa. Surface area loss was found to be greater than 50%, while canopy cover has diminished linearly over the period studied, with the risk of disappearance of the woodland increasing in the same magnitude as borer population density. The highest wood borer population densities observed corresponded to stands with an average canopy cover loss of 1.68% a year, indicating a risk of completely losing the forest cover in the short term (10–30 years). The proposed tree injury index was successful in categorizing the size of the insect population, and seems to be a useful indicator for describing the relationship between the two variables. According to this indicator, woodlands with more than 10% of trees with severe or very severe injuries are at risk. Follow-up work should be undertaken to investigate long-term demographic changes in wood borer populations, and management practices should be developed to reduce the population size, minimize forest loss and preserve these relict oak trees in unconnected landscapes, The field work was undertaken within projects funded by the Council for the Environment of the Regional Government of Andalusia We received strong support from Rubén Fernández Villarán and Cristina Pérez-Carral for the management and decisions about the GIS. We are also grateful to E. Paramio, L. Borruecos, J. M. Caraballo, J. A. Domínguez-Feria, D. Barja, F. J. García, C. Malia, A. Rincón, M. Salado, M. A. Gay and especially R. Tapias and P. Alesso for their help with the monitoring carried out. Further, we would like to thank all of the landowners for the permission granted to work on their estates

La morfología de la carrasca (Quercus rotundifolia Lam.) varía ampliamente entre poblaciones e individuos, desde portes arbóreos a arbustivos de distintos tamaños, número de tallos y densidades foliares. Estos cambios están relacionados tanto con las perturbaciones climáticas y el manejo humano como con las enfermedades sufridas a lo largo del tiempo. En la Península Ibérica una de las principales preocupaciones desde los años 80 es la “seca” de los Quercus. Enfermedad compleja promovida por el hongo Phytophthora cinnamomi Rands. Sus síntomas principales son la defoliación y el secado de las puntas de las ramas, llegando a causar en ocasiones la muerte de los individuos. Nuestras hipótesis de partida fueron a) que la estructura morfológica de la carrasca podría estar vinculada con la aparición de la “seca” y b) que tanto la morfología como el estado (afectada o no por la “seca”) de las mismas podrían determinar el efecto sobre otras especies vegetales o procesos del ecosistema, como la fijación de carbono. Se seleccionaron 43 carrascas dispersas en una matriz arbustiva presente en el P.N. del Carrascal de la Font Roja (Alcoy, Alicante) que diferían tanto en la morfología como en su estado y se analizó a) si la altura, el área que ocupa, el número de tallos y la biomasa de rebrotes estaban relacionados con su estado, y b) si los cambios de la morfología y el estado dan lugar a cambios en la riqueza de especies de plantas y otros atributos del ecosistema tales como biomasa y abundancia vegetal, carbono orgánico (CO) del suelo, capacidad de almacenamiento de agua, reciclado de nutrientes y resistencia a la erosión. El índice de área foliar (LAI) se utilizó como variable representativa del estado; menor LAI correspondió a una probabilidad mayor de presentar “seca”. Los resultados mostraron que la estructura morfológica no estaba vinculada a la presencia de la seca. Además, se observó un efecto negativo de la altura sobre la abundancia y la biomasa vegetal, que los suelos bajo las carrascas sanas presentaban mayor capacidad de almacenamiento del agua y reciclado de nutrientes y, por último, que el estado modula el efecto del número de tallos sobre el CO y la riqueza (en las carrascas afectadas se observa un efecto negativo sobre el CO del suelo y positivo sobre la riqueza). Nuestro estudio demuestra que los efectos de la carrasca sobre su entorno son diversos y dependen de factores que se pueden modificar mediante el manejo (como su morfología) o su estado de salud. La morfologia de la carrasca (Quercus rotundifolia Lam.) varia àmpliament entre poblacions i individus, les carrasques poden ser des de arbres fins matolls de diferents mides, nombre de tiges i densitats foliars. Aquests canvis estan relacionats tant amb pertorbacions climàtiques i maneig humà, com amb malalties patides al llarg del temps. A la Península Ibèrica, una de les preocupacions principals des dels anys 80 es la “seca” dels Quercus. És una malaltia complexa, promoguda pel fong Phytophthora cinnamomi Rands. Els seus símptomes principals són la defoliació i assecat de les branques, arribant fins i tot a causar la mort de l’arbre. Les nostres hipòtesis de partida van ser: a) que la morfologia de la carrasca està vinculada amb l’aparició de la “seca”, i b) que tant la morfologia com l’estat (afectada o no per la “seca”) de les carrasques determinen l’efecte sobre altres espècies vegetals i processos de l’ecosistema, com són la fixació de carboni. Vam seleccionar 43 carrasques disperses a una matriu arbustiva present en el P.N. del Carrascal de la Font Roja (Alcoi, Alacant) que es diferenciaven tant en la morfologia com en l’estat, analitzant: a) si l’alçària, l’àrea que ocupa, el nombre de tiges i la biomassa de rebrots estaven relacionats amb l’estat, i b) si els canvis en la morfologia i estat donen lloc a canvis en la riquesa d’espècies, la biomassa i nombre d’individus de plantes, el contingut de carboni en el sòl, la capacitat per emmagatzemar aigua, reciclar nutrients o resistir a l’erosió. L´índex d’àrea foliar (LAI) es va utilitzar com a variable representativa de l’estat; menys LAI correspon amb individus que han patit la “seca”. Els resultats van mostrar que la morfologia de la carrasca no estava relacionada amb la presència de la “seca”. També, vam observar un efecte negatiu de l’alçària en l’abundància i biomassa vegetal, i que els sòls sota les carrasques sanes presentaven millor capacitat de retenir l’aigua i reciclar els nutrients i, per últim, que l’estat altera l’efecte del nombre de tiges en el contingut de carboni i la riquesa (les carrasques sanes amb més tiges tenen més carboni al sòls i menys espècies vegetals, al contrari de les carrasques que han patit la “seca”). L’estudi demostra que els efectes de la carrasca sobre el seu voltant són diversos i dependents de factors que podem modificar amb el maneig (com la morfologia) i el seu estat de salut. Oak morphology (Quercus rotundifolia Lam.) varies between populations and individuals; they can be either trees or shrubs, with contrasting sizes, number of stems and leaf densities. These changes are related to climatic disturbances and human management and to diseases suffered over time. In the Iberian Peninsula, one of the main concerns since the 1980s has been the "oak decline". This is a complex disease promoted by a fungal infection (Phytophthora cinnamomi Rands ). Its main symptom is the progressive fall of leaves and death of upper branch tips, sometimes causing the death of the whole individual. Our hypotheses were: a) oak morphology can be linked to the "oak decline", and b) oak morphology and its state (affected or not by the "oak decline") determine the effect of oaks on other plant species or on ecosystem processes, such as carbon fixation. We selected 43 oaks present in the “P.N. del Carrascal de la Font Roja” (Alcoy, Alicante), that differed in their morphology and state. We analyzed a) if the height, the area, the number of stems and the biomass of sprouts were related to its state, and b) if the changes in morphology and state affected understorey plant species richness and other ecosystem attributes such as biomass and plant abundance, soil organic carbon (CO), water storage capacity, nutrient cycling and resistance to erosion. The leaf area index (LAI) was used as a representative variable of the state; lower LAI corresponded to a higher probability of presenting "oak decline". We concluded that the morphological structure was not linked to the presence of the "oak decline". However, we observed a negative effect of height on understorey plant abundance and biomass, that the soils under healthy oaks had a greater capacity for water storage and nutrient recycling and, lastly, that the state modulated the effect of the number of stems on CO and understorey richness (in affected oaks: a negative effect on soil CO and a positive effect on richness). Our study shows that oak effects on its environment are diverse and depend on factors that can be modified by management (such as its morphology) or its health state. Esta investigación ha sido financiada por el Ministerio de Ciencia, Innovación y Universidades, del Gobierno de España, mediante el proyecto I+D+I «Retos investigación» del programa estatal de I+D+I orientada a los retos de la sociedad “Identificando las consecuencias funcionales de cambios en la biodiversidad a varias escalas espaciales” (FOBIASS; RTI2018-098895-a-i00) y la ayuda Ramón y Cajal (RyC-2016-20604).

12 páginas.- 4 figuras.- 4 tablas.- 114 referencias.- Supplementary data to this article can be found online at https://doi.org/10.1016/j.soilbio.2022.108560., The loss of tree health is a global concern with many unknown cascading impacts on the diversity and function of forest ecosystems. Specifically, it is uncertain how the process of tree decline and mortality driven by exotic pathogens might alter the soil microbiome. Here we combined high-throughput sequencing, neighborhood models, and network analysis to explore the impacts of the decline of a Mediterranean tree species, Quercus suber, on the diversity, composition and network structure of soil fungal and bacterial communities in forests invaded by the exotic pathogen Phytophthora cinnamomi. The belowground footprint of pathogen-driven tree decline implied an increase in the taxonomic and phylogenetic diversity of both bacteria and fungi, but also a severe reduction of tree-symbiotic fungi and Proteobacteria known to have positive effects on plant growth and disease suppression. Moreover, we detected alterations of the topology of soil microbial networks in declining tree neighborhoods (lower connectivity, higher modularity), with implications for ecosystem function. Our findings reveal the large impacts that moderate levels of tree decline can have on the soil microbiome of invaded forests, and highlight the recovery of a functionally diverse and highly connected soil microbiome as a key target in the restoration of these disturbed systems., This research was supported by the Ministerio de Ciencia e Innovación (MICINN) projects INTERCAPA (CGL2014-56739-R) and MICROFUN (RTI2018-094394-B-I00). AJMP was supported by a post-doctoral fellowship funded by the Portuguese Foundation for Science and Technology (SFRH/BPD/111015/2015), JDB by a FPI-MEC grant (BES-2012-055113) and EVS by a FPU-MICINN grant (FPU16/04616).

Highlights • Mutually competitive interactions prevail in pairwise cultures of AOD bacteria. • In vitro growth of brenneria goodwinii is improved by bacterial competition. • Co-culturing of AOD bacteria indicates evolving improved fitness of B. goodwinii. • B. goodwinii and R. victoriana can collaborate in vitro to outcompete G. quercinecans., Brenneria goodwinii, Rahnella victoriana and Gibbsiella quercinecans are three bacterial species frequently isolated together from oak displaying symptoms of Acute Oak Decline (AOD), which include weeping patches on trunks. All three bacterial species play a role in lesion formation in the current episode of AOD in Britain, although B. goodwinii is the most dominant. The ongoing research into stem lesion formation characteristic of this polybacterial syndrome has been focussed primarily on the pathogenicity, identification and taxonomy of these bacteria. As all three species were newly classified within the past ten years, there are many unanswered questions regarding their ecology and interactions with each other. To determine the effect of bacterial interactions on fitness in vitro, we examined pairwise (diculture) and multispecies (triculture) interactions between B. goodwinii, R. victoriana and G. quercinecans in oak leaf media microcosms. Additionally, the effect of co-culturing on the evolution of these species was determined and the evolved B. goodwinii strains were examined further by whole genome sequencing. Our results indicate that B. goodwinii thrived in monoculture with significantly higher viable cell counts than the other two species. Additionally, B. goodwinii performed well in pairwise culture with mutually competitive interactions observed between B. goodwinii and R. victoriana, and between B. goodwinii and G. quercinecans. In the multispecies triculture, B. goodwinii and R. victoriana appeared to exhibit co-ordinated behaviour to outcompete G. quercinecans. After four weeks B. goodwinii grown in co-culture with the other two species developed greater evolved fitness than the strain grown in monoculture as reflected by the increased viable cell counts. The competitive interactions taking place between the threes species indicated evolving improved fitness of B. goodwinii in vitro, that gave it a growth advantage over both R. victoriana and G. quercinecans which showed no significant changes in fitness. Overall, B. goodwinii gains greater benefit in terms of fitness from in vitro competitive interaction with the other two species., Graphical abstract Image, graphical abstract.

Biscogniauxia mediterranea is the causal agent of charcoal disease, affecting oak decline under the trigger of various biotic and abiotic factors, including climate change. Here, we report the genome assembly of an Italian B. mediterranea strain obtained using hybrid sequencing technologies combining long and short reads.

Acute Oak Decline (AOD) is complex syndrome affecting Britain’s keystone native oak species, (Quercus robur L. and Q. petraea L. (Matt.) Liebl.), in some cases causing mortality within five years of symptom development. The most distinguishable symptom is weeping stem lesions, from which four species of bacteria have been isolated: Brenneria goodwinii, Gibbsiella quercinecans, Lonsdalea britannica and Rahnella victoriana. We do not yet know where else these bacteria exist, and little is known about the relationship of the wider oak leaf microbiome (phyllosphere) to acute oak decline. Here we investigate whether incidental evidence from a large oak genome re-sequencing dataset could be used to detect these bacteria in oak foliage, and whether bacterial incidence co-varied with AOD status or location. Oak leaves and buds were sampled from 421 trees at five sites in England. Whole genomic DNA from these samples was shot-gun sequenced with short reads. Non-oak reads were extracted from these data and queried to microbial databases. Reads uniquely matching AOD-associated bacterial genomes were found to be present on trees from all five sites and included trees with active lesions, trees with historic lesions and trees without AOD symptoms. The abundance of the AOD-associated bacteria did not differ between tree health categories but did differ among sites. We conclude that the AOD-associated bacteria may be members of the normal oak microbiome, whose presence on a tree is not sufficient to cause AOD symptoms.

Holm oak decline is a complex phenomenon mainly influenced by the presence of Phytophthora cinnamomi and water stress. Plant functional traits (PTs) are altered during the decline process — initially affecting the physiological condition of the plants with non-visual symptoms and subsequently the leaf pigment content and canopy structure — being its quantification critical for the development of scalable detection methods for effective management. This study examines the relationship between spectral-based PTs and oak decline incidence and severity. We evaluate the use of high-resolution hyperspectral and thermal imagery (< 1 m) together with a 3-D radiative transfer model (RTM) to assess a supervised classification model of holm oak decline. Field surveys comprising more than 1100 trees with varying disease incidence and severity were used to train and validate the model and predictions. Declining trees showed decreases of model-based PTs such as water, chlorophyll, carotenoid, and anthocyanin contents, as well as fluorescence and leaf area index, and increases in crown temperature and dry matter content, compared to healthy trees. Our classification model built using different PT indicators showed up to 82% accuracy for decline detection and successfully identified 34% of declining trees that were not detected by visual inspection and confirmed in a re-evaluation 2 years later. Among all variables analysed, canopy temperature was identified as the most important variable in the model, followed by chlorophyll fluorescence. This methodological approach identified spectral plant traits suitable for the detection of pre-symptomatic trees and mapping of oak forest disease outbreaks up to 2 years in advance of identification via field surveys. Early detection can guide management activities such as tree culling and clearance to prevent the spread of dieback processes. Our study demonstrates the utility of 3-D RTM models to untangle the PT alterations produced by oak decline due to its heterogeneity. In particular, we show the combined use of RTM and machine learning classifiers to be an effective method for early detection of oak decline potentially applicable to many other forest diseases worldwide., Data collection was partially supported by the QUERCUSAT (CGL2013-40790-R) and ESPECTRAMED (CGL2018-86161-R) projects, part of the Spanish Research Agency, Ministry of Science and Innovation. A. Hornero was supported by research fellowship DTC GEO 29 “Detection of global photosynthesis and forest health from space” from the Science Doctoral Training Centre (Swansea University, United Kingdom). P. North was supported by the NERC National Centre for Earth Observation (United Kingdom). F.J. Ruiz-Gómez was supported by a post-doctoral fellowship of the Junta de Andalucía (Spain) and the European Social Fund 2014-2020 Program (DOC_0055).

Oaks are dominant and key tree species in Mediterranean forest ecosystems. However, in recent decades, oak forests have been heavily impacted by oak decline, a worldwide phenomenon exacerbated by climate change. The charcoal disease agent Biscogniauxia mediterranea is involved in the decline of Mediterranean oak formations in a variety of contexts. Here, we investigated the impact and role of B. mediterranea in the decline of oaks in Castelfidardo Forest, a relict wood of the late Holocene and a Site of Community Importance. We established five plots within which we recorded tree positions, any symptoms and signs of decline, association of B. mediterranea to declining trees, and deadwood and associated mycota. Of 471 oaks inspected, 7.0% showed brownish exudates on the stems, 46.9% showed epicormic shoots along the main trunk, and 24.4% showed black carbonaceous stromata on diseased branches and trunks. The decline was most severe for Quercus cerris, which comprised plots #4 and #5, at 50.0% (81/162 trees) and 29.0% (33/114), respectively, then for Quercus robur for plot #3, at 40.0% (38/95), and finally for Quercus pubescens for plots #1 and #2, at 13.7% (7/51) and 12.3% (6/49), respectively. Bark tissue was collected from trees with charcoal cankers via microscopy examination and identified by mycological and molecular methods. This investigation revealed a close association between oaks with pronounced reduction of vitality and incidence of B. mediterranea. Deadwood was equally distributed among the five plots, and was heavily colonized by Basidiomycota. The high incidence of the charcoal canker pathogen B. mediterranea appeared to be related to environmental stresses. However, the absence of silvicultural management, high competition among physiologically mature trees, and the geographic isolation of this residual forest may have predisposed oaks to decline.

Oaks are a dominant and key tree species in Mediterranean forest ecosystems. However, in recent decades, oak forests have been heavily impacted by oak decline, a worldwide phenomenon exacerbated by climate change. The charcoal disease agent Biscogniauxia mediterranea is involved in the decline of Mediterranean oak formations in a variety of contexts. Here, we investigated the impact and role of B. mediterranea in decline of oaks in Castelfidardo Forest, a relict wood of the late Holocene and a Site of Community Importance. We established five plots within which we recorded the tree positions, any symptoms and signs of decline, association of B. mediterranea to declining trees, and the deadwood and associated mycota. Of 471 oaks inspected, 7.0% showed brownish exudates on the stems, 46.9% showed epicormic shoots along the main trunk, and 24.4% showed black carbonaceous stromata on diseased branches and trunks. The decline was most severe for Quercus cerris, which comprised plots #4 and #5, at 50.0% (81/162 trees) and 29.0% (33/114), respectively; then for Quercus robur for plot #3, at 40.0% (38/95); and finally for Quercus pubescens for plots #1 and #2, at 13.7% (7/51) and 12.3% (6/49), respectively. Bark tissue was collected from trees with charcoal cankers, with microscopy examination and identification by mycological and molecular methods. This investigation revealed close association between oaks with pronounced reduction of vitality and incidence of B. mediterranea. The deadwood was equally distributed among the five plots, and was heavily colonized by Basidiomycota. The high incidence of this oak-weakening pathogen B. mediterranea appears to be related to stress conditions (e.g., water scarcity, prolonged drought). However, absence of silvicultural management, high competition among physiologically mature trees, and the geographic isolation of this residual forest might have predisposed these oaks to decline.

We studied the maternally inherited chloroplast DNA polymorphism at three microsatellite loci of 157 Quercus robur trees from 38 native populations in Lithuania. We found high diversity of eight haplotypes from the Balkan lineage A (frequency 0.75) and the “German” subbranch of the Balkan lineage A (freq. 0.12), western and eastern Italian lineages C (freq. 0.05 and 0.06, respectively), and Iberian lineage B (freq. 0.03). The haplotypes were geographically well structured (among population differentiation index PhiPT = 0.30, the p-value &lt, 0.001) that is unexpected for such a small territory as Lithuania. We raised a hypothesis on historical overexploitation of oaks by eliminating certain haplotypes in Lithuania, following a drastic felling of oak forests over the last few centuries.

The decline of cork oak trees in North-West of Algeria was supposed to be caused by a combination of primary or predisposing factors, and secondary or opportunistic factors. There is a broad consensus about the role of water scarcity and nutrients in the primary causes, given the similarity of symptoms of cork oak decline and of chronic water deficits. To identify and characterize the cork oak decline in M’sila forest, a cork oak mortality index was determined for each transience area using a GIS approach and a linear regression model formulated by analyzing the interactions between the attributes of station (competition of superior and inferior floor); and allowing a justification of cork oaks mortality. The mortality index is significantly high in the invasive shrub plots and where the Aleppo pine density is very high; in which competition for soil water between the trees and the inferior floor increases. The lowest mortality value characterized by a lower density of Aleppo pine and herbaceous inferior floor.

In the Iberian Peninsula, Oak Decline (hereafter, OD) is becoming a serious and frequently occurring disease in Mediterranean oaks. Decline processes seem to involve multiple biotic and abiotic factors, which combine to reduce the vigour of oak trees often causing death. However, the exact causes of its extension are still unknown and therefore, given the ecological, economic and social relevance of these trees in Mediterranean countries it is crucial to develop tools that allow us to anticipate its occurrence and to reduce its expansion. In this sense, the present work aims to (i) unravel the relative role of environmental factors on the distribution of one of the most important phenomena that threat the biodiversity of the Iberian oaks, and (ii) to produce a spatially explicit model of OD risk, to assist conservation managers dealing with this phenomenon. To this, we have used a dataset of OD foci gathered during the period 2015–2017 by the program “Methodology for the inventory and monitoring of oak masses affected by the decline of oak in the southwest of Castilla y Leon” (this region is beginning to suffer the damages of this disease). In total, 68 locations were used to assess relationships with environmental factors (topographic conditions, abiotic stress conditions and human influence) using maximum entropy models (hereafter, MaxEnt) and variance-partitioning. OD distribution seems to be principally influenced by land-use (mainly dehesas), followed by dryer areas and areas with low slope gradients facing south or southeast. The resulting model has been used to produce a detailed OD risk map in central-western Spain. Our modelling approach may contribute to inform conservation planning and to establish the adequate management policy for Iberian oak dehesas, by helping to identify regions where the risk of OD is high.

Declines are a distinctive category of tree disease, complex to define and quantify and challenging to mitigate due to their multiple causes and heterogeneous tree response patterns. In many parts of Europe oak decline syndromes are severely impacting tree health and having a measurable economic impact on forestry. In the UK the impact of periodic oak declines is expanding against a backdrop of multiple environmental pressures, to levels capable of threatening the UK’s native oak woodland. Here we explore the growth histories of oak trees at a site symptomatic of Chronic Oak Decline (COD), in the South of England; Speculation Cannop in the Forest of Dean, Gloucestershire. The dendrochronological picture at the site reveals that trees with current external COD symptoms have shown suppressed growth, in relation to the regional average, from early on in their lives. Moreover, there is an amplified reduction in minimum ring width in Symptomatic trees as compared to a healthy subsample of Control trees, likely to be heavily dominated by reduced latewood width in affected trees, as decline sets in. Broadly, the site reveals the initial appearance of decline, roughly 40 years after planting, in 1860. There is considerable variability in the later decline history pattern in Symptomatic trees but there are clusters of decline episodes in the 1920s, 1960s, 1980s and 1990s at this site. The Control trees are not always unaffected but rather show growth releases after each historical decline phase. The trees that currently show external decline symptoms do not have a history of these growth releases. We conclude that investigating the tree ring growth histories at sites impacted by COD could provide an important management tool, and ring width histories of trees at affected sites should be used in the identification of the decline predisposing factors, that a management strategy requires.

The Zagros Mountains forests extend across 11 provinces in Iran and constitute approximately 40.0% of the country’s woodlands. These forests have important soil conservation and water regul...

Widespread decline and mortality of white oaks (Quercus alba) occurred in Missouri Ozark forests between 2011 and 2017. Symptoms included rapid crown death with bronzing of leaves, retention of dead leaves, crown dieback and thinning, and loss of large limbs within one year of death. Decline and mortality were associated with hillside drainages and fit descriptions of European oak forests predisposed to decline by pathogenic Phytophthora species. A survey was performed at two locations in 2014 and 2015 to assess the distribution of dead and declining white oaks, and the occurrence and distribution of Phytophthora species. Multiple Phytophthora species were detected, including P. cinnamomi, P. cactorum, P. europaea, and P. pini. P. cinnamomi was the most common and widely distributed species among plots at both locations. The detection of P. cinnamomi at the base of white oaks was not associated with poor crown vigor. However, more quantitative survey techniques are necessary to clearly evaluate this relationship. P. cinnamomi kills fine roots of white and red oaks in North America and has been associated with the decline of white oaks in the United States (Ohio) and other countries. Further studies are needed to determine the importance of P. cinnamomi in oak decline within the Ozark highlands.

At the study area serious oak decline was detected from 1979-80 in a mixed oak forest, an area covered by a sessile oak–Turkey oak forest (Quercetum petraeae-cerridis). The shrub community was divided into low (lower than 1.0 m in height) and high shrub layer (≥ 1.0 m). The goals of this study were to determine the conditions of shrub layer and analyse the possible changes in the shrub layer after 4 decades of the serious oak decline. In 2017, 17 shrub species were continuously observed in the understory. The density of shrub layer was 25,103 specimens ha-1. The significant part of shrubs lived (91.6%) in the low shrub layer, with only a small part of them (8.4%) forming the high shrub layer. The most common species of the shrub community was Euonymus verrucosus with 1989 shoots in the monitoring plot. The mean height and mean diameter of the high shrub species changed between 1.29-8.74 m and between 0.81-9.61 cm. The mean cover of the high shrub species changed between 0.56 m2 and 12.67 m2. Our results suggest that three woody species, Acer campestre, Acer tataricum and Cornus mas responded successfully to the oak decline.